The fact is, we’re going to go on offense here. Because the president has raided the Medicare trust fund to the tune of $716 billion to pay for a massive expansion of government known as Obamacare.

This will be an uphill battle for the GOP, for two reasons.

First, Democrats are more trusted to handle the issue of Medicare. That is, they “own” the issue. See, for example, my piece on campaign agendas (especially Figure 1). To cite some more recent data, a February GW Battleground Poll found that 52% of respondents trusted Democrats to handle “Social Security and Medicare,” while 43% trusted Republicans. A June 2011 poll found that 47% of respondents had “more confidence” in the Democrats’ ability to handle Medicare, while 40% had more confidence in Republicans.

Second, although perceptions of which party owns an issue can change, they usually will not change during the short window of a campaign. Take 1988 for example. In this election, Michael Dukakis tried to emphasize national defense. George H.W. Bush emphasized jobs and declared that he would be the “education president.” Both were attempting to “trespass” on the other party’s territory. How’d that work out for them? Political scientists Bruce Buchanan and Helmut Norpoth studied those strategies and found:

Voters tended to attribute Bush’s slogans and promises about education and jobs to Dukakis, and attribute Dukakis’s promises about national defense to Bush. They relied on stereotypes of issue ownership—“if someone wants to improve education, he must be a Democrat”—rather than pay attention to the specific promises of Bush and Dukakis.

In my work, I find that parties often trespass by finding dimensions of issues that play to the party’s ideology. So a Republican might talk about education by emphasizing vouchers. Democrats might talk about crime by talking about prevention rather than punishment (see, e.g., David Holian’s study of Bill Clinton).

With regard to Romney-Ryan and Medicare, you could imagine how the GOP might try to do this. For example, they could talk about “reforming Medicare” as a means to reducing the budget deficit, since that is what Ryan has proposed anyway and since the deficit is an issue more associated with the GOP. Sure, Obama will counter-attack—calling the “reform” dismantlement, etc.—but at least the battle will be partly fought on the GOP’s turf.

But to go toe-to-toe on “who wants to cut Medicare more”? That strikes me as a much harder sell for the Republican ticket.